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what caused the turbine jet crash??!!!!!

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what caused the turbine jet crash??!!!!!

Old 04-09-2012, 05:49 AM
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lenhard2007
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Default what caused the turbine jet crash??!!!!!

ok so this is its 4th flight and when i was over the runway i threw out my gear then i went into a turni threw my flaps. when i threw my flaps she crashed.... after looking at the flap servos and connecting them they were fine.... now this is one of two things....one... hinge failure or the guy that built it had too many y harnesses. he had three of them..or what do u think????? please help. they receiver is fine and connection was good.
www.youtube.com/watch
Old 04-09-2012, 05:54 AM
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AndyAndrews
 
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Default RE: what caused the turbine jet crash??!!!!!

Sorry for your loss. It looks like you entered into a split flap situation to me. One flap goes down and the other stays up. Acts just like an aleron.
Old 04-09-2012, 06:34 AM
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Default RE: what caused the turbine jet crash??!!!!!

Sorry for yor loss of the airplane... I have to ask, from personal experience.... Was Crow involved in the full flap set up, and did you inspect all clevis's ( Flap and Aileron ) post crash.. I tend to agree with Andy, one flap failed to deploy. Your departure and roll rate was much more aggressive than mine was on the KingCat... Also check to see if the flap servo connector at the wing joint when assembling was not plugged in backwards... I've seen that before, and would have gone unnoticed unless flaps were checked on taxi out or take off laps were used.


Regards,

Danno
Old 04-09-2012, 06:47 AM
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flyinfool1
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Default RE: what caused the turbine jet crash??!!!!!

I see two possibilities.

1. What Andy described with only one flap coming down. Could have been servo came unplugged, linkage broke, or servo failed. If it was a case of only one flap coming down, it was the left flap that failed.

2. Simple stall. You were going very slow and making a tight high bank turn, and then deployed flap in the turn. After the stall instinct is to hold full up elevator trying to save it so the stall would carried all of the way to the ground.

Do you have some down elevator mixed with the flap? It appeared that the plane pitched down just before it rolled over as in maybe only one flap went down and the down trim kicked in.
This seems the most likely of the 2 possibilities to me.

Granted you had very little time to react, But you need to always have in the back of your mind the what if scenarios. In a case like this, you flipped a switch and something bad happened, put the switch back where it was.
If it was a stall, the only way to save it is with down elevator to get speed up and then pull out. Again you did not have much time, but sometimes it only takes a couple of MPH more (only a few feet of dive) to get the wing flying again. It is hard to make the brain dive when you are already headed down.

Usually when making a slow turn you need more rudder and less aileron to keep the wing more level so it can make some lift.

This is something that I always practice at high altitude to see what the stall characteristics and recovery of a plane are in different attitudes.
Old 04-09-2012, 06:50 AM
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Gary Arthur
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Default RE: what caused the turbine jet crash??!!!!!

I do not think there is enough information. For example, was this your fourth flight of the day? Or the fourth flight on the aircraft? Did you do a control surface check before the flight and if so, were the ailerons and flaps working correctly?

I usually do a flight control check, where I put a slight load on the surface with one finger. This not only shows the surfaces moving in theright direction, but will tell you how good the gear train is.

For example, if you had a bouncy landing the flight before, you could have induced a heavy load on the gear train. One tooth could be compromised. A slight load could detect the bad tooth.
Old 04-09-2012, 06:53 AM
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Gary Arthur
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Default RE: what caused the turbine jet crash??!!!!!


ORIGINAL: flyinfool1


1. What Andy described with only one flap coming down. Could have been servo came unplugged, linkage broke, or servo failed. If it was a case of only one flap coming down, it was the left flap that failed.
It appeared to roll to the right, suggesting the right flap failed.
Old 04-09-2012, 07:05 AM
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Default RE: what caused the turbine jet crash??!!!!!

That sudden/abrupt nose down change from straight and level flight at what seems like way over stall speed, outrules stall in my opinion. if only one flap did lower, I believe the airplane would start a roll only, not pitch down so violently.

To me, it looks more like a total signal loss. Have you tested the RX batteries under load? The forces on the flaps can be quite substansial.
Old 04-09-2012, 07:15 AM
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Gary Arthur
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Default RE: what caused the turbine jet crash??!!!!!


ORIGINAL: kimhey

That sudden/abrupt nose down change from straight and level flight at what seems like way over stall speed, outrules stall in my opinion. if only one flap did lower, I believe the airplane would start a roll only, not pitch down so violently.

To me, it looks more like a total signal loss. Have you tested the RX batteries under load? The forces on the flaps can be quite substansial.
The plane had rolled to the right and was inverted. Then it apears a pull up on the elevator caused the dive.
Old 04-09-2012, 07:30 AM
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Default RE: what caused the turbine jet crash??!!!!!


ORIGINAL: Gary Arthur

The plane had rolled to the right and was inverted. Then it apears a pull up on the elevator caused the dive.
I watched the vid a few more times. The plane was making a left turn, the right wing tip was visible above the fuse, at the time of roll over the right wingtip was still above the fuse and got higher as it rolled to inverted. This means that the plane did in fact roll left. If it was thought by the pilot as the two previous posters, to have rolled right then it is possible that the wrong correction was given and when it was thought to have rolled back to upright it had in actuality rolled inverted and the up elevator would then have been a bad thing.
Old 04-09-2012, 07:37 AM
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erbroens
 
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Default RE: what caused the turbine jet crash??!!!!!

A downwind turn!


Old 04-09-2012, 08:08 AM
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Jack Diaz
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Default RE: what caused the turbine jet crash??!!!!!

Kimhey, I agree with you.

Lenhard, sorry !! We all know what you feel.

In my opinion, the load of the flaps lowered the battery voltage to a point where even if the receiver is still working, the servos are dead.
There was no abrupt roll or pitch change. All failed smooth and gradual. Dead servos.
If the turbine was off at impact (no fire), and Lenhard didn't shut it off: the voltage went so low that the ECU shut it off.
If the voltage at the receiver is still close to 4 volts, the ECU doesn't shut down for low voltage. But again, servos are dead.

I have seen this happen a few times before, for the same cause. And with the model describing the exact same trajectory. And happens when you lower the flaps.
In one occasion, the batteries were OK, but the regulator failed when lowering the flaps.

BTW, I have simulated all these scenarios at my shop. There is a thread somewhere here that my son wrote on this subject.
We compared No Fly Voltages of Li-Po vs. Li-Ion and they are quite different. There is a table of comparison in that thread. I will try to find it.

Jack

Old 04-09-2012, 08:40 AM
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Gary Arthur
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Default RE: what caused the turbine jet crash??!!!!!

ORIGINAL: flyinfool1


ORIGINAL: Gary Arthur

The plane had rolled to the right and was inverted. Then it apears a pull up on the elevator caused the dive.
I watched the vid a few more times. The plane was making a left turn, the right wing tip was visible above the fuse, at the time of roll over the right wingtip was still above the fuse and got higher as it rolled to inverted. This means that the plane did in fact roll left. If it was thought by the pilot as the two previous posters, to have rolled right then it is possible that the wrong correction was given and when it was thought to have rolled back to upright it had in actuality rolled inverted and the up elevator would then have been a bad thing.
I disagree. At 2:17 of the video, you will see the plane has actually leveled off meaning rolling to the right from the original left hand bank. By 2:18 you can see the left wingtip rising, a short pause, then more roll to the right and inverted.

Once inverted, up elevator was applied causing the dive. Then as it continues down, it also keeps rolling to the right....
Old 04-09-2012, 08:56 AM
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Default RE: what caused the turbine jet crash??!!!!!


ORIGINAL: flyinfool1


ORIGINAL: Gary Arthur

The plane had rolled to the right and was inverted. Then it apears a pull up on the elevator caused the dive.
I watched the vid a few more times. The plane was making a left turn, the right wing tip was visible above the fuse, at the time of roll over the right wingtip was still above the fuse and got higher as it rolled to inverted. This means that the plane did in fact roll left. If it was thought by the pilot as the two previous posters, to have rolled right then it is possible that the wrong correction was given and when it was thought to have rolled back to upright it had in actuality rolled inverted and the up elevator would then have been a bad thing.
Looks like it rolls right to me.... A roll and then pull on the stick.

Mike

Old 04-09-2012, 09:12 AM
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Jack Diaz
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Default RE: what caused the turbine jet crash??!!!!!

Gary and Mike: the roll direction was never mentioned by Lenhard. So, I wouldn't jump to atribute disorientation as a cause.
Althought an interesting discussion, I don't think it is relevant for the crash analysis.
The plane dived and rolled by itself.
If it was battery system related (as I presume), there is a usefull lesson to be learned by all of us.
I would focus the analysis in that direction.


jack
Old 04-09-2012, 10:01 AM
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Default RE: what caused the turbine jet crash??!!!!!

HI all, My first impression was a receiver shut down, I completely agree with Jack.
PS. never drop flaps in a turn, pitch change , should be adjusted in the first few flights.
PS. slow servo on Flaps will decrease a spike in voltage, compared to fast servo speed.

See you all in Toledo.
Rcpete
Old 04-09-2012, 10:05 AM
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lenhard2007
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Default RE: what caused the turbine jet crash??!!!!!

ok guys thanks for your response. the plane was level when i applied flaps. this was its fourth flight altogher. i just bought the plane a week ago and when i hooked everything up i noticed one of flaps just "flaping" it was going up and down all by its self. so i took everything apart and found a wire that was causing it," or thats what i thought it was"i didalot of test and it never happened again. i run a lipo 2cell 2100mh for ecu and a 2000nimh 6 voltfor the servos, ive always done this and never had an issue. my radio and battery are fine and every servo works under load. know what does concern me is this thing had 3 y harnesses in it. and ive heard turbine dont act right with them thats why u get matchboxes, you can get away with one y, but 3????????
i never installed crow or any up or down elevator to the flap setting.
also did a through ground check before flight....always do with my turbines.
Old 04-09-2012, 10:06 AM
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Gary Arthur
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Default RE: what caused the turbine jet crash??!!!!!


ORIGINAL: Jack Diaz

Gary and Mike: the roll direction was never mentioned by Lenhard. So, I wouldn't jump to atribute disorientation as a cause.
Althought an interesting discussion, I don't think it is relevant for the crash analysis.
The plane dived and rolled by itself.
If it was battery system related (as I presume), there is a usefull lesson to be learned by all of us.
I would focus the analysis in that direction.


jack
Jack

I agree that regardless of roll direction, a roll did occur when flaps were deployed. So regardless or direction, the flap, servo, battery, linkage, throw, speed etc created a roll that the pilot did not recover from.

Setting up flaps can sometimes be overlooked for items such as speed etc.

Old 04-09-2012, 10:21 AM
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Jack Diaz
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Default RE: what caused the turbine jet crash??!!!!!

Lenhard: I think you gave us the answer !!!!!
A 2000mA NiMH won't be enough juice for four flights.
On the conservative side, consider that you use 500mA per flight, and should never go beyond 50% of the battery capacity. You have two safe flights with that battery.

Besides, charging NiMH is VERY tricky. Most chargers think that they are full when they are not.

Use Li-Po's or 123 or Li-Ion, with a good charger. And redundancy is of utmost importance.

Jack
Old 04-09-2012, 10:39 AM
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Default RE: what caused the turbine jet crash??!!!!!

Where does it say that the battery wasn't freshly charged? In any case, depending on the model, a good 2000mAh Nimh might easily get 4 flights.

IMO there isn't enough info to make any positive statement about what happened. Did it go into failsafe? Was the model responding to any inputs after the flap deployment?


The video reminds me a bit of the crash of the big B52 in the UK which caused by disorientation. Try and work out if the model is rolling right or left just before impact[&o]

[youtube]http://www.youtube.com/watch?v=gPGFaXqzitc[/youtube]
Old 04-09-2012, 10:56 AM
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Default RE: what caused the turbine jet crash??!!!!!


ORIGINAL: Jack Diaz

Lenhard: I think you gave us the answer !!!!!
A 2000mA NiMH won't be enough juice for four flights.
On the conservative side, consider that you use 500mA per flight, and should never go beyond 50% of the battery capacity. You have two safe flights with that battery.

Besides, charging NiMH is VERY tricky. Most chargers think that they are full when they are not.

Use Li-Po's or 123 or Li-Ion, with a good charger. And redundancy is of utmost importance.

Jack
I tend to agree with Jack on this point. NiMh will false peak most of the time on the smart chargers. You have to restart the charger several times to get it to take a full charge. I'm sure you can adjust the M/volt peak detection value in the charger to help with this, but the advise Jack gives it very sound.. Get away from NiMh !!!! The other part I think need clarification is what Radio system you are useing. ( I'm not going there at all !!! ) However, if the Y-Harnesses you speak of are the JR Amplified Y's , flying 2.4mhz, there in lies you problem... I got away with that ONE flight in Mississippi 2 years ago when I switched from 72mhz to 2.4, and did not change the Y's and it showed it self on start up and pre taxi on second flight attempt and I caught it. It would have cost me the airplane. It also had servo jitter and strange deflections on flaps and ailerons.. I also had Matchbox's in the mix. Amplified Y's and 2.4 do NOT mix. !!!!


Danno
Old 04-09-2012, 11:06 AM
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lenhard2007
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Default RE: what caused the turbine jet crash??!!!!!

guys the battery was full and that was the only flight of the day. she had four flights on her but only one that Sat. i fly on futuab 2.4 10c with a 14 channel receiver and its still bends to my tx
Old 04-09-2012, 11:08 AM
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Default RE: what caused the turbine jet crash??!!!!!

Seemed pretty fast for a stall...more like a strong asymmetric control
input. If the rx battery died the moment you selected flaps down...it could look like that.
Sorry for your loss!
TP.
Old 04-09-2012, 11:12 AM
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Default RE: what caused the turbine jet crash??!!!!!


ORIGINAL: lenhard2007

guys the battery was full and that was the only flight of the day. she had four flights on her but only one that Sat. i fly on futuab 2.4 10c with a 14 channel receiver and its still bends to my tx

What about the Y's ??? Are they amplified ??

Dan
Old 04-09-2012, 11:16 AM
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Gary Arthur
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Default RE: what caused the turbine jet crash??!!!!!


ORIGINAL: lenhard2007

guys the battery was full and that was the only flight of the day. she had four flights on her but only one that Sat. i fly on futuab 2.4 10c with a 14 channel receiver and its still bends to my tx
Since this occured on the first flight of the day, did you do a control surface check of all surfaces including the flaps prior to flying?
Old 04-09-2012, 11:19 AM
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Default RE: what caused the turbine jet crash??!!!!!

A lot of the new chargers today also have a time limit and a charge limit preset in them. you have to go in and reprogam them or atleast check them. we have had some crashes at our field (non jets) but still applies here. they would charge up flight packs before the days flying. they would charge a 2000 mah pack at 400-500 mah. well at 400 mah that would take over 2 hours. well they chargers they were using had a two hour limit built in as a default setting. so when the charger stopped charging they thought it was fully chatged.


it all comes down to knowing your equipment.

When i fly larger more expensive planes I charge/discharge packs of any battery type before it ever goes in a plane so you know the real capacity. then you have to Measure how power you use per flight. See how many times you want to fly then double that MAH rating of the pack(s)

i agree that a single 2000 Mah NiMh pack is to small for a large jet. i bet you are using over 400 mah per 8 minute flight. 4 flights and thats 1600 mah right there. you add in a a pack that isnt fully charged and the fact that even if was fully charged you used 70% of its charge. the voltage is low and way low when a load is placed on it. i think flap failed and the plane went in failsafe with low voltage.

Was the battery pack yours or did it come with the plane?

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